Various camera-shake correction apparatuses (image blurring correction apparatuses) have hitherto been proposed that enable blurring on an imaging surface to be prevented and sharp imaging to be achieved despite the occurrence of camera shake (vibration) when a still image is captured.
Optical methods such as a sensor shifting method and lens shifting method, and software methods in which camera shake is corrected by image processing by means of software, are known as camera-shake correction methods.
A sensor shifting method is disclosed in Patent 2004-274242 (Patent Literature 1), for example. A digital camera disclosed in Patent Literature 1 has a configuration in which an imaging device (CCD) is movable centered on a reference position (center) by means of an actuator. The actuator performs camera-shake correction by moving a CCD according to camera shake detected by a vibration sensor. The CCD is located in a CCD moving section. The CCD can be moved by means of the CCD moving section within an XY plane perpendicular to a Z axis. The CCD moving section comprises three main members: a base plate fixed to a housing, a first slider that moves in the X-axis direction with respect to the base plate, and a second slider that moves in the Y-axis direction with respect to the base plate.
In a sensor shifting method such as disclosed in Patent Literature 1, the CCD moving section (movable mechanism) is large. Consequently, it is difficult to apply a sensor-shifting type of camera-shake correction apparatus to a small camera for mobile phone use from a size (external shape and height) standpoint.
Next, lens shifting methods will be described.
Patent 2009-145771 (Patent Literature 2), for example, discloses a camera-shake correction apparatus that includes a camera-shake correction unit that drives a corrective lens. The camera-shake correction unit is provided with a base plate, which is a fixed member, a movable lens barrel that holds the corrective lens in a movable fashion, three spheres held between the base plate and the movable lens barrel, a plurality of elastic bodies supporting the movable lens barrel elastically against the base plate, two coils fixed to the base plate, and two magnets fixed to the movable lens barrel.
Also, Patent 2006-65352 (Patent Literature 3) discloses an “image blurring correction apparatus” that corrects image blurring by controlling the movement of a specific lens group (hereinafter referred to as “corrective lens”) in an imaging optical system (image formation optical system) comprising a plurality of lens groups in two directions perpendicular to each other in a plane perpendicular to the optical axis. In the image blurring correction apparatus disclosed in Patent Literature 3, the corrective lens is supported so as to be able to move vertically (in the pitch direction) and laterally (in the yaw direction) with respect to a fixed frame via a pitching movement frame and yawing movement frame.
Patent 2008-26634 (Patent Literature 4) discloses a “camera-shake correction unit” that includes a corrective optical member that corrects blurring of an image formed by an imaging optical system by moving in a direction that intersects the optical axis of the imaging optical system. In the case of a corrective optical member disclosed in Patent Literature 4, a lens holding frame that holds a corrective lens is supported so as to be able to move in the pitch direction and yaw direction with respect to a housing barrel via a pitch slider and yaw slider.
Patent 2006-215095 (Patent Literature 5) discloses an “image blurring correction apparatus” that can move a corrective lens by means of a small driving force and can perform fast and high-precision image blurring correction. The image blurring correction apparatus disclosed in Patent Literature 5 is provided with a holding frame that holds a corrective lens, a first slider that supports this holding frame so as to be able to slide in a first direction (pitch direction), a second slider that supports the holding frame so as to be able to slide in a second direction (yaw direction), a first coil motor that drives the first slider in the first direction, and a second coil motor that drives the second slider in the second direction.
Patent 2008-15159 (Patent Literature 6) discloses a lens barrel provided with a camera-shake correction optical system installed so as to be able to move in a direction perpendicular to the optical axis. In the camera-shake correction optical system disclosed in Patent Literature 6, a movable VR unit located inside a VR body unit holds a corrective lens (a third lens group), and is installed so as to be able to move within an XY plane perpendicular to the optical axis.
Patent 2007-212876 (Patent Literature 7) discloses an “image blurring correction apparatus” in which image blurring can be corrected by making a corrective lens held in a movable frame movable in mutually perpendicular first and second directions with respect to the optical axis of the lens system, and controlling the optical axis of the corrective lens by means of a drive section so as to coincide with the optical axis of the lens system.
Patent 2007-17957 (Patent Literature 8) discloses an “image blurring correction apparatus” that corrects image blurring by driving a corrective lens for correcting blurring of an image formed by a lens system by means of operation of a lens drive section in a first direction and second direction that are directions perpendicular to the optical axis of the lens system and also mutually perpendicular. In the image blurring correction apparatus disclosed in Patent Literature 8, the lens drive section is provided located toward a direction perpendicular to the optical axis of the corrective lens.
Patent 2007-17874 (Patent Literature 9) discloses an “image blurring correction apparatus” in which image blurring can be corrected by making a corrective lens held in a movable frame movable in a first direction and second direction that are directions perpendicular to the optical axis of the lens system and also mutually perpendicular, and controlling the optical axis of the corrective lens so as to coincide with the optical axis of the lens system. This image blurring correction apparatus disclosed in Patent Literature 9 is provided with a drive section having a coil and magnet that are made movable in a relative fashion. Either the coil or the magnet is fixed to a movable frame, and the other is fixed to a supporting frame that supports the movable frame in a movable fashion. Also, this image blurring correction apparatus disclosed in Patent Literature 9 is provided with a first Hall device that detects position information relating to a first direction of the corrective lens by detecting magnetic force of the magnet, and a second Hall device that detects position information relating to a second direction of the corrective lens by detecting magnetic force of the magnet.
The lens-shifting types of image blurring correction apparatuses (camera-shake correction apparatuses) disclosed in above Patent Literature 2 through 9 all have a structure whereby a corrective lens is adjusted by being moved in a plane perpendicular to the optical axis. Therefore, a problem with an image blurring correction apparatus (camera-shake correction apparatus) having such a structure is that its structure is complex and it is not suitable for miniaturization. That is to say, as with an above-described sensor-shifting type of camera-shake correction apparatus, it is difficult to apply a lens-shifting type of camera-shake correction apparatus to a small camera for mobile phone use from a size (external shape and height) standpoint.
A software method is disclosed, for example, in Patent HEI11-64905 (Patent Literature 10). In the method disclosed in Patent Literature 10, a captured image is made static when an imaging apparatus becomes static and free from camera shake by eliminating a noise component from detection section detection results, and calculating specific information necessary for correction of image blurring due to shaking of the imaging apparatus from a detection signal from which this noise component has been eliminated.
However, a problem with this software method disclosed in Patent Literature 10 is that image quality degrades in comparison with an above-described optical method. Also, a software method has the disadvantage of taking a long time, since it includes both imaging time and software processing time.
In order to solve the above problems, a camera-shake correction apparatus (image blurring correction apparatus) has been proposed that corrects camera shake (image blurring) by shaking an actual lens module (camera module) that holds a lens and imaging device (image sensor). Such a method will be referred to here as an “optical unit tilting method.”
“Optical unit tilting methods” will now be described.
Patent 2007-41455 (Patent Literature 11), for example, discloses an “optical apparatus image blurring correction apparatus” that is provided with a lens module that holds a lens and imaging device, a frame structure that supports this lens module so as to be rotatable by means of a rotation shaft, a drive section (actuator) that rotates the lens module with respect to the frame structure by providing driving force to a driven section (rotor) of the rotation shaft, and a force application section (leaf spring) that forces the drive section (actuator) against the driven section (rotor) of the rotation shaft. The frame structure comprises an inner frame and outer frame. The drive section (actuator) is disposed so as to come into contact with the driven section (rotor) of the rotation shaft from a direction perpendicular to the optical axis. The drive section (actuator) comprises a piezoelectric device and a rotation-shaft-side operating section. The operating section drives the rotation shaft by means of vertical oscillation and flexion oscillation of the piezoelectric device.
Also, Patent 2007-93953 (Patent Literature 12) discloses a “camera-shake correction apparatus” in which a camera module integrating an imaging lens and image sensor is housed in a housing, and the camera module is pivoted in the housing so as to be able to rock freely about a first shaft and second shaft that are perpendicular to the imaging optical axis and intersect each other at right angles, and camera shake during still image capture is corrected by controlling the overall attitude of the camera module within the housing according to shaking of the housing detected by a camera-shake sensor. The camera-shake correction apparatus disclosed in Patent Literature 12 is provided with a center frame that supports the inner frame to which the camera module is fixed so as to be able to rock freely about the first shaft from the outside thereof, an outer frame that is fixed to the housing and supports the center frame so as to be able to rock about the second shaft from the outside thereof, a first drive section that is incorporated into the center frame and rocks the inner frame about the first shaft according to a camera-shake signal from a camera-shake sensor (first sensor module that detects camera shake in the pitch direction), and a second drive section that is incorporated into the outer frame and rocks the center frame about the second shaft according to a camera-shake signal from a camera-shake sensor (second sensor module that detects camera shake in the yaw direction). The first drive section comprises a first stepping motor, a first reduction gear train that decelerates the rotation thereof, and a first cam that rotates integrally with a final gear and rocks the inner frame via a first cam follower provided on the inner frame. The second drive section comprises a second stepping motor, a second reduction gear train that decelerates the rotation thereof, and a second cam that rotates integrally with a final gear and rocks the center frame via a second cam follower provided on the center frame.
Furthermore, Patent 2009-288770 (Patent Literature 13) discloses an “imaging optical apparatus” capable of dependably correcting shaking by improving the configuration of an imaging unit drive mechanism for shake correction for the imaging unit. The imaging optical apparatus disclosed in Patent Literature 13 comprises, on the inside of a fixed cover, an imaging unit (movable module), and a shake correction mechanism for performing shake correction by displacing this imaging unit. The imaging unit is for moving a lens in the optical axis direction. The imaging unit comprises a movable body that holds a lens and fixed diaphragm on the inside, a lens drive mechanism that moves this movable body in the optical axis direction, and a support on which the lens drive mechanism and movable body are mounted. The lens drive mechanism is provided with a lens drive coil, lens drive magnet, and yoke. The imaging unit is supported by a fixed body by means of four suspension wires. At two places on either side of the optical axis are provided a first imaging unit drive mechanism and second imaging unit drive mechanism for shake correction, the two of which form a pair. In these imaging unit drive mechanisms, an imaging unit drive magnet is held on the movable body side, and an imaging unit drive coil is held on the fixed body side.
Patent 2007-142938 (Patent Literature 14) discloses a portable information terminal having a function for correcting camera shake during imaging using a gyroscope or suchlike angular velocity sensor. In order to perform correction of captured image shake, it is necessary to set a reference pitch axis and yaw axis that are mutually perpendicular in a plane that is perpendicular to the optical axis of a camera lens, and detect the angular velocity of both rotation with the pitch axis as the central axis of rotation and rotation with the yaw axis as the central axis of rotation. Patent Literature 14 discloses the disposition of a first gyroscope that detects the rotational angular velocity of rotation about the pitch axis, and a second gyroscope that detects the rotational angular velocity of rotation about the yaw axis, on a side surface of an imaging apparatus.
Also, Patent 2008-20668 (Patent Literature 15) discloses a lens drive apparatus that drives a lens in the optical axis direction. This lens drive apparatus disclosed in Patent Literature 15 is provided with a plurality of coiled bodies fixed to the outer periphery of a lens support, and a magnet section disposed facing the coiled bodies. The magnet section is provided with magnetic poles N and S that are polarized into an N pole and S pole in a radial direction and differ in the lens optical axis direction. The coiled bodies are provided corresponding to the polarity of the magnet section, and currents flow in mutually opposite directions in adjacent coiled bodies.